Whistling or squeaking noise from MT prop

About six months ago we installed a new three blade MT prop. Soon after, we started to hear a faint squealing noise that sounded like a loose alternator belt. Upon further investigation it turned out that our alternator pulley was touching the cowling. I think the slightly heavier prop might have exacerbated the situation. We pulled the prop, again and installed a shorter alternator belt. Performed test run up and still had the squeaking at idle and when taxiing.

We figured that we had a bad alternator bearing and replaced the alternator. Performed test run and still had squeaking.

At this point we notice that if you bring the idle up to about 1100 RPMs the squeaking goes down but now we have enough oil pressure to cycle the prop which made the squeaking almost go away.

Called MT prop who were incredibly helpful as usual. When I told him what was going on they replied with. "Oh, yes those blades whistle at idle".

So although it had nothing to do with the alternator at least now I don't have a hole in my cowling from the alternator pulley. And we have a new alternator.

I wanted to post this as I haven't seen anything anywhere about composite prop blades whistling.

dan

I have the whistle also at or near 1000 RPM.
At first I thought it was the alternator belt, checked the tension and all ok.
I too noticed that the whistle changed with the RPM or if I taxi with head or tail wind.

Me too

I have experienced the same thing and I also thought it might be my alternator or the belt.

I usually only notice it when I taxi back to my hangar at low RPM. A slight change in RPM and the noise goes away.

Yup, can always tell when my buddy with the 3MT is in the area!

I just last month had a 3B MT9 installed during my prop strike repair. My hearing sucks with a constant ringing (too many years on military Flightlines). If I ever hear the whine (whistle) at least I now won’t go chasing alternator problems that most likely aren’t there. Thanks for the post.

PS: love this propeller however it did move my cg aft a little.

Yes the MT whistle!! I’ve got it too. Definitely sounds like something rubbing somewhere but it’s the air screaming in fear!!

Same thing happens on my -8. The 3-bladed MT prop squeaks at low RPM. It was a real head-scratcher at first. I thought it was a loose belt or even the spinner touching the cowl. The guys at MT in Deland explained what's happening and I don't sweat it anymore. Perfectly normal, apparently.

Which one?

Just out of curiosity....is it the -9 or -12 or both? My -9 is still in the crate. (I just hear it humming in there from time to time )

Skykingbob said:

Just out of curiosity....is it the -9 or -12 or both? My -9 is still in the crate. (I just hear it humming in there from time to time )

Click to expand...

I have the -9-

have the -12, and sure love that whistle.
Canopy slid back, hair (?) in the wind, left elbow resting nonchalantly on the fuse side, right hand waving to the chicks, and that lovely surreal turbine like music, or whistle, what a life

Sure would not want any other prop on my baby.